FATES : Understanding rapid climate change in the recent past

05.03.2015

Around 20,000 years ago, our planet emerged from the last ice age. The huge glaciers receded and, as the climate warmed up, forests began to spread. The hunter-gatherer way of life was gradually superseded by sedentary farming. This was a time of great upheavals, when episodes of rapid warming alternated with significantly colder periods, sometimes lasting several decades.

This is a fascinating, but still not well understood, period for climate scientists. What changes in temperature, precipitation, ocean circulation, atmospheric conditions and vegetable cover accompanied these climate swings? Is it possible to play back the film of this period, year by year, using indices from our natural climate ‘archives’ such as lake and ocean sediment, corals, ice cores, pollen or the concretions – stalactites, stalagmites, etc – found in caves? This is the goal of the FATES (which stands for FAst climate changes, new Tools to understand and simulate the evolution of the Earth System) project, on which 85 scientists from a number of laboratories run by the University of Paris-Saclay are collaborating.

The idea is that, by developing innovative methods of dating and analysing samples, this programme will enable researchers to decipher these past changes in the Earth’s climate more accurately. This will in turn allow them to test and improve the current climate models.

New from old!

“Climate specialists usually want to go as far back in time as possible. This time however we’re hoping to create a high-resolution picture of some more recent periods of great upheaval,” explains Valérie Masson-Delmotte from the Laboratory for Climate and Environmental Sciences (LSCE), one of the six project coordinators.

In the first phase, there are no plans to carry out any new drilling or send out any new field expeditions. Lots of samples are already available at the laboratories and the idea is now to select the material most likely to provide high-value information and analyse it using a new generation of instruments.

“Our project is based on developing innovative equipment to achieve a more refined analysis of the available archives and to be able to date them more accurately,” says the LSCE researcher. The new measurements exercise will concentrate on a few short periods of up to 250 years that were marked by the most rapid climate change.

Testing the models

One of the most valuable outcomes of this exercise will be to compare these results with the calculations made using climate models. Several climate modelling groups will therefore be able to compare their simulations of this recent deglaciation period with the data gathered from the natural archives.

Can we simulate these past climate upheavals with the same models as those being used to anticipate future risks? Are some models more realistic than others?

The scientists working on the FATES project will also be modelling the parameters measured, including pollen and various water and carbon isotopes, with the aim of understanding the most rapid changes observed during this past deglaciation so as to shed light on current and future climate phenomena.

Anticipating future change

At the end of the last period of glaciation, the Earth’s average surface temperature was 5°C cooler than it is today.

The global climate then warmed at an average pace of the order of 1°C every 1,000 years, but the warming process was in fact much faster during certain periods in certain regions.

“Changes in the circulation of the Atlantic Ocean had opposing impacts in the two hemispheres, brought about by a switching effect in heat transfer. In Greenland for example, this led to warming of as much as 5°C in 100 years,” reveals Valérie Masson-Delmotte.

And the scientists are expecting similar local warming effects by the end of this century.

Changes in the circulation of the Atlantic Ocean had opposing impacts in the two hemispheres, brought about by a switching effect in heat transfer.

What exactly are the reasons for those violent shifts in the ocean currents? Might they occur again in the future? Is it possible to simulate precisely the speed at which European forests reacted to these variations and will react once again to future climate change?

By looking back and forth at climates past and future, the FATES project researchers hope to be able to get a better idea of our ability to calculate the speed of the environmental changes that are on the way.

“ Studying the end of the last glaciation period will enable us to gain a better understanding of the workings of the climate and to test our climate models against the fastest and most intensive changes known to us. ”

Valérie Masson-Delmotte

from the Laboratory for Climate and Environmental Sciences (LSCE), who is one of the project coordinators